Electrosurgical apparatus and method of tissue ablation

ABSTRACT

An electrosurgical apparatus for treating fluid-filled biological growths by replacing the fluid within the growth with a substance that assists in delivering treatment energy. The treatment energy may be microwave energy or may be thermal energy derived from microwave energy. The apparatus comprises an instrument having a radiating tip portion, and a fluid delivery mechanism for transporting fluid to and from a treatment zone located around the radiating tip portion. The fluid delivery mechanism comprises a rigid insertion element arranged to extend into the treatment zone, whereby fluid can be aspirated from the treatment zone, and a substance injected into the treatment zone to replace the aspirated fluid. The injected substance has dielectric properties selected to facilitate uniform delivery of treatment energy to biological tissue in the treatment zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/481,411, filed on Jul. 26, 2019, which is a National Stage entry ofInternational Application No. PCT/EP2018/061316, filed May 3, 2018,which claims priority to Great Britain Patent Application No. 1707112.7,filed May 4, 2017. The disclosures of the priority applications arehereby incorporated in their entirety by reference.

FIELD OF THE INVENTION

The invention relates to an electrosurgical apparatus and method forablating biological tissue using microwave energy. In particular, theinvention relates to the ablation of biological growths, such as cystsor tumours, especially where such growths contain fluid. The inventionmay find particularly use in treating pancreatic cysts or tumours.

BACKGROUND TO THE INVENTION

It is inherently difficult to gain access to growths such as tumours orcysts in the pancreas due to the location of the pancreas and itsproximity to other organs. Additionally, the margins between a growth'sboundary and the pancreatic wall are often very small. Because of this,there is a high risk of collateral damage to other organs duringsurgical procedures to treat or remove pancreatic tumours or cysts. As aresult, many treatment options are employed, such as chemotherapy,radiotherapy, and different types of surgery. Surgical procedures caninvolve partial or total pancreatectomy (removal of the pancreas), stentplacement or bypass surgery (e.g. to relieve a blocked bile duct) orenucleation (removal of just the tumour/cyst). Depending on the type ofsurgery, the pancreas may be accessed by open surgery (e.g. using alarge incision in the abdomen), or via a keyhole incision using alaparoscope.

The morphology of cysts and tumours within the pancreas is varied andcan consist of a solid mass, one or more open voids, or a mixture ofsolid mass and open voids. The open voids (or sacs) are filled withcystic fluids such as serous fluid or mucinous fluid. The fluid-filledsacs within a single tissue growth may be in communication with eachother (i.e. there are passages connecting them), or may be separate(i.e. without any connection between them).

A known method for detecting and imaging pancreatic cysts and tumours isendoscopic ultrasound (EUS). In this method, an endoscope is insertedinto the patient's mouth and advanced through the oesophagus and stomachuntil it is in the vicinity of the duodenum. An ultrasound probe on theendoscope is used to obtain high quality images of the surroundingorgans. Because of the proximity of the pancreas to the duodenum, verydetailed ultrasound images of the pancreas can be obtained.Additionally, a pancreatic biopsy can be obtained during an EUSprocedure, using a fine hollow needle on the endoscope. The needle isused to pierce the duodenal or stomach wall at an appropriate locationso that it can be inserted into the pancreas. The ultrasound images canbe used to accurately guide the needle to a desired location in thepancreas, such as a specific mass or cyst. Fluid from the pancreas orgrowth is then aspirated through the needle and collected so that it maybe examined. This procedure is known as fine-needle aspiration (FNA).

SUMMARY OF THE INVENTION

At its most general, the present invention provides an electrosurgicaltechnique for effectively treating fluid-filled biological growths byreplacing the fluid within the growth with a substance that assists indelivering treatment energy. The treatment energy may be microwaveenergy or may be thermal energy derived from microwave energy, e.g. bydielectric heating.

By appropriately selecting the substance which is to be injected intothe growth void, transmission of microwave and/or thermal energy to thegrowth tissue can be optimised, thus providing more efficient growthablation. Conventional microwave ablation instruments usually have asymmetrical radiation profile, making the ablation of irregular ornon-symmetrical growths difficult. By filling the void with a substancefor transmitting energy to growth tissue, irregular or non-symmetricalgrowths can be ablated more effectively. The electrosurgical device canbe configured to be fed through the working channel of an endoscope, sothat it can be used to carry out minimally invasive surgical procedures.

According to a first aspect of the invention, there is provided anelectrosurgical apparatus for treating a biological growth that containsa fluid-filled sac, the apparatus comprising: an electrosurgicalinstrument for delivering microwave energy into biological tissue, theelectrosurgical instrument comprising: a coaxial cable for conveyingmicrowave energy; and a radiating tip portion disposed at a distal endof the coaxial cable to receive microwave energy from the coaxial cable;and a fluid delivery mechanism for transporting fluid to and from atreatment zone located around the radiating tip portion, wherein thefluid delivery mechanism comprises: a flexible fluid conveying conduitthat extends along the coaxial cable, and a rigid insertion element influid communication with a distal end of the fluid conveying conduit andarranged to extend into the treatment zone, wherein the fluid deliverymechanism is arranged: to aspirate fluid from the treatment zone, and toinject a substance into the treatment zone to replace the aspiratedfluid, and wherein the substance has dielectric properties selected tofacilitate uniform delivery of treatment energy to biological tissue inthe treatment zone.

In use, the treatment zone may include a fluid-filled sac containedwithin a biological growth. The fluid delivery mechanism may be arrangedto replace biological fluid in the fluid-filled sac with the substancebefore microwave energy is applied to treat. The treatment energy may betargeted at the biological tissue that surrounds (i.e. provides an innerwall of) the fluid-filled sac. Use of the substance may enable thatbiological tissue to receive uniform treatment.

The radiating tip portion may comprise a microwave antenna. The antennamay be a conventional monopole antenna formed on the end of the coaxialfeed cable. An inner conductor of the coaxial feed cable may beconnected to a radiating tip of the microwave antenna from whichmicrowave energy can radiate. The radiating tip may include one or moredielectric materials to provide dielectric loading of the antenna, inorder to enhance or shape the energy emission profile of the microwaveantenna. In certain embodiments, the electrosurgical instrument mayinclude multiple monopole antennae connected to the coaxial feed cable,in order to emit energy over a broader area. The multiple monopoleantennae may be connected to the coaxial cable by a suitable powersplitter arrangement. The antennae may be radially extendable to occupya larger volume in the treatment zone.

The electrosurgical instrument can be used to apply microwave energy tomatter in its vicinity, such as biological tissue, fluids or othermaterials. Microwave energy can cause dielectric heating in biologicaltissue, which can be used to ablate tissue in a localised volume aroundthe antenna. Therefore, by inserting the antenna directly into a growthsuch as a cyst or a tumour, microwave energy can be applied to thegrowth tissue in order to ablate it.

Herein, the terms “proximal” and “distal” refer to the ends of theenergy conveying structure further from and closer to the treatment siterespectively. Thus, in use the proximal end is closer to a generator forproviding the microwave energy, whereas the distal end is closer to thetreatment site, i.e. the patient.

The term “conductive” is used herein to mean electrically conductive,unless the context dictates otherwise.

The term “longitudinal” used below refers to the direction along theinstrument channel parallel to the axis of the coaxial transmissionline. The term “lateral” refers to a direction that is perpendicular tothe longitudinal direction. The term “inner” means radially closer tothe centre (e.g. axis) of the instrument channel. The term “outer” meansradially further from the centre (axis) of the instrument channel.

The term “electrosurgical” is used in relation an instrument, apparatusor tool which is used during surgery and which utilises microwaveelectromagnetic (EM) energy. Herein, “microwave EM energy” may meanelectromagnetic energy having a stable fixed frequency in the range 300MHz to 100 GHz, preferably in the range 1 GHz to 60 GHz. Preferred spotfrequencies for the microwave EM energy include 915 MHz, 2.45 GHz, 5.8GHz, 14.5 GHz, 24 GHz. 5.8 GHz may be preferred.

The fluid delivery mechanism enables fluid to be aspirated from a voidin a growth, for example cystic fluid from a void in a cyst. Followingaspiration of the fluid, the fluid delivery mechanism is configured toinject a substance into the void. The fluid delivery system may beconfigured to detect that a volume of fluid has been aspirated, and inresponse to detecting a particular volume, it is configured to injectthe substance. In certain embodiments, the fluid delivery mechanism isconfigured to inject a volume of the substance into the void in thegrowth equal to a volume of the fluid aspirated from the void in thegrowth. This ensures that the amount of substance injected into the voidin the growth will completely fill the void and maximises the contactarea between the substance and the growth tissue. The substance can thentransmit energy to all parts of the internal walls of the void.Controlling the amount of substance injected in this manner also ensuresthat the void is not overfilled, which could cause the growth to ruptureand substance to flow out from the void.

The rigid insertion element may comprise a hollow needle. The hollowneedle may be positioned at a distal end of the fluid deliverymechanism. The hollow needle may have a sharp end so that it can be usedto pierce the wall of an organ and be inserted at a desired locationinto the organ. For example, the needle may be used to pierce throughthe duodenal wall so that the needle may be inserted into the pancreas.Fluid can be aspirated through the hollow needle so that it passesthrough the fluid conduit.

The fluid delivery mechanism may be separate from the electrosurgicalinstrument, or it may be integrated with the electrosurgical instrument.In embodiments where they are separate, the electrosurgical instrumentand fluid delivery mechanism may be configured to be inserted separatelyinto the working channel of an endoscope. For example, the fluiddelivery mechanism can first be inserted into the working channel of anendoscope to aspirate fluid from a void in a growth and, if appropriate,inject a substance into the growth. The fluid delivery mechanism canthen be removed from the working channel and the electrosurgicalinstrument inserted into the working channel. The antenna of theelectrosurgical instrument can then be inserted into the aspirated voidof the growth so that ablation of the growth tissue may be carried out.

In embodiments where the fluid delivery mechanism is integrated with theelectrosurgical instrument, the fluid delivery mechanism andelectrosurgical instrument can be fed simultaneously into the workingchannel of an endoscope. In certain embodiments, the rigid insertionelement is mounted near the distal end of the electrosurgicalinstrument. For example the rigid insertion element may be secured tothe radiating tip portion. The fluid conduit and coaxial feed cable maybe housed in a single protective sheath running along part or all oftheir lengths. The integration of the two components provides a compactdevice and simplifies ablation procedures, as it does not requiredifferent components to be inserted into or removed from the workingchannel of an endoscope during an ablation procedure.

In another example, the coaxial cable may comprise an inner conductor,an outer conductor, and a first dielectric material separating the innerconductor and outer conductor. The inner conductor may be hollow toprovide a passageway for the fluid delivery mechanism. The rigidinsertion element may be in fluid communication with the flexible fluidconveying conduit via the passageway. The rigid insertion element (e.g.hollow needle) may be slidably mounted in the passageway.

The rigid insertion element may be movable between an exposed positionwhere it protrudes beyond the distal end of the electrosurgicalinstrument, and a retracted position in which it is set back from thedistal end of the electrosurgical instrument. The rigid insertionelement may be moved between the two positions using one or more controlwires. This enables the rigid insertion element to be deployed only whenthe user wishes to make use of the fluid delivery system, so that therigid insertion element does not cause any accidental injuries when thefluid delivery system is not in use.

The distal end of the electrosurgical instrument may also include asheath or protective hull which covers the rigid insertion element whenit is in the retracted position, to further improve safety.

The fluid delivery mechanism may include two separate containers at aproximal end thereof. A first container may be for receiving theaspirated fluid. A second container may be for holding the substance tobe injected. While the fluid is aspirated, the first container can beconnected to the fluid conduit at the proximal end of the fluid deliverymechanism, so that aspirated fluid can be collected in the firstcontainer. Optionally, the first container can include a mechanism fordetecting an amount of fluid collected (e.g. by measuring its weightand/or volume). The fluid is aspirated through the needle and the fluidconduit by creating a suction force in the fluid conduit, for example byusing a syringe or a pump. To inject the substance, the first containeris disconnected from the fluid conduit and the second container isconnected to the fluid conduit. The substance may be caused to flow downthe fluid conduit and rigid insertion element using a piston attached tothe second container. The connection and disconnection of the containerscan be carried out manually by the user, or can be carried outautomatically by a controller, for example using a controllable valvesystem.

The electrosurgical instrument may be configured to, following theinjection of the substance into the void in the growth, delivermicrowave energy to the substance. This causes microwave energy and/orthermal energy to be transmitted via the substance to the growth tissue.This allows energy to be transferred from the antenna to the growthtissue more efficiently. Additionally, it enables irregular ornon-symmetrical growths to be ablated more effectively, as the substancein the void causes the energy emitted by the antenna to be distributedmore evenly around the walls of the void. The substance which isinjected into the void can enhance the transmission of energy to growthtissue in several ways.

In one example, the substance may serve to transmit thermal energy fromheated portions of tissue or substance to cooler portions of tissue orsubstance. The transmission of thermal energy to the growth tissue isachieved by using a substance which has a high dielectric loss factor atthe microwave energy frequency used. In other words, the substance mayconsist of or comprise a dielectric fluid, such as de-ionised water orsaline. When microwave energy is applied to the substance, the substanceheats up and imparts thermal energy to the surrounding growth tissue,thus causing ablation of the growth tissue.

In contrast, the substance may provide dielectric loading for theantenna, in order to improve the efficiency of microwave energy deliveryto the growth tissue. For example, if a substance is used which has alow dielectric loss factor at the microwave energy frequency, thesubstance will act as a conduit for efficiently transmitting microwaveenergy to the growth tissue. The dielectric loss factor is related tothe imaginary part of a material's permittivity, and is indicative ofenergy dissipation in the material.

The substance may also be selected to effectively extend the radiatingtip portion in order to produce a non-symmetrical radiation profile inorder to match the shape of the void.

The substance may include a variety of fluids, gels or other suitablematerials. In certain embodiments, the substance may be selected totransition from a liquid phase to a solid phase during application ofmicrowave energy to the treatment zone. The hardening of the substancemay be caused by a small rise in temperature arising from theapplication of microwave energy. Preferably the substance has a lowdielectric loss factor at the microwave energy frequency, so that thehardened substance may act as an efficient means for transmitting themicrowave energy from the microwave antenna into the wall of the void.This enables the microwave energy to be distributed around the walls ofthe void, even in cases where the void is irregular or non-symmetricalin shape, so that the growth may be effectively ablated.

The electrosurgical instrument may comprise an ultrasound probe forproducing images of a patient's internal organs. The images produced bythe ultrasound probe may be used to guide the growth ablation device toa desired location inside the patient. For example the ultrasound imagesmay be used to guide the hollow needle to a cyst in the pancreas. Theultrasound probe may for example be mounted near the distal end of theelectrosurgical instrument.

The electrosurgical apparatus discussed above may form part of ancomplete electrosurgical system. The system may further comprise agenerator for generating the microwave energy, and a surgical scopingdevice for non-percutaneous insertion into a patient's digestive tract.The surgical scoping device may have an instrument channel running alongits length, wherein the electrosurgical instrument and fluid deliverymechanism are conveyed within the instrument channel of the surgicalscoping device. The coaxial cable is connected to receive the microwaveenergy from the generator.

Also disclosed herein is a method for treating a biological growth thatcontains a fluid-filled sac, the method comprises: non-percutaneouslyinserting an instrument cord of a surgical scoping device into apatient's digestive tract, the surgical scoping device having aninstrument channel running along its length; conveying anelectrosurgical instrument and a fluid delivery mechanism along theinstrument channel of the surgical scoping device, wherein theelectrosurgical instrument comprises a coaxial cable for conveyingmicrowave energy, and a radiating tip portion disposed at a distal endof the coaxial cable to receive microwave energy from the coaxial cable,and wherein the fluid delivery mechanism comprises a flexible fluidconveying conduit that extends along the coaxial cable, and a rigidinsertion element in fluid communication with a distal end of the fluidconveying conduit; extending the rigid insertion element into afluid-filled sac contained within a biological growth located at thedistal end of the instrument cord; aspirating fluid from thefluid-filled sac; injecting a substance into the fluid-filled sac toreplace the aspirated fluid; and delivering microwave energy to theradiating tip portion, wherein the substance has dielectric propertiesselected to facilitate uniform delivery of treatment energy tobiological tissue surrounding the fluid-filled sac. Any feature of theelectrosurgical apparatus and system discussed herein my be utilised inthe method.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention are discussed below with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic diagram of an electrosurgical apparatus for tissueablation that is an embodiment of the invention;

FIG. 2 is a schematic cross-sectional view of a distal end of anablation instrument suitable for use in the invention;

FIG. 3 is a schematic cross-sectional view of a distal end of anotherablation instrument suitable for use in the invention;

FIG. 4 is a schematic illustration of a tissue ablation method that isan embodiment of the invention; and

FIG. 5 is a schematic diagram of a fluid delivery mechanism which mayform part of an electrosurgical apparatus according to the invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a complete electrosurgical apparatus100 that is an embodiment of the invention. The apparatus 100 isarranged to treat a fluid-filled biological growth (e.g. a cyst ortumour, referred to herein simply as a “growth”, which contains one ormore sacs of fluid). The apparatus 100 is capable of removing fluid froma void in a biological growth, injecting a substance into the void inthe growth, and ablating the growth by applying microwave energy. Asdiscussed below, the injected substance facilitates the delivery ofenergy to the cyst. The delivered microwave energy may be used to ablatebiological tissue at an inside wall of the cyst, e.g. to remove and/orprevent regrowth of unwanted tissue, or to stop or prevent more fluidfrom filling the voids. In some embodiments, after treatment, thesubstance may be removed from the void.

The system 100 comprises a generator 102 for controllably supplyingmicrowave energy. A suitable generator for this purpose is described inWO 2012/076844, which is incorporated herein by reference. The generatormay be arranged to monitor reflected signals received back from theinstrument in order to determine an appropriate power level fordelivery. For example, the generator may be arranged to calculate animpedance seen at the distal end of the instrument in order to determinean optimal delivery power level.

The generator 102 is connected to an interface joint 106 by an interfacecable 104. The interface joint 106 is also connected to a fluid deliverydevice 108, such as a syringe, via a fluid conduit 107. If needed, theinterface joint 106 can house an instrument control mechanism that isoperable by sliding a trigger 110, e.g. to control longitudinal (i.e.back and forth) movement of one or more control wires or push rods (notshown). If there is a plurality of control wires, there may be multiplesliding triggers on the interface joint to provide full control. Thefunction of the interface joint 106 is to combine the inputs from thegenerator 102, fluid delivery device 108 and instrument controlmechanism into a single flexible shaft 112, which extends from thedistal end of the interface joint 106.

The flexible shaft 112 is insertable through the entire length of aworking (instrument) channel of a surgical scoping device 114, such asan endoscope, gastroscope, laparoscope or the like. The flexible shaft112 has a distal assembly 118 (not drawn to scale in FIG. 1 ) that isshaped to pass through the working channel of the surgical scopingdevice 114 and protrude (e.g. inside the patient) at the distal end ofthe surgical scoping device's working channel. The distal end assembly118 includes a microwave antenna for delivering microwave energy and ahollow needle (not shown) fluidly connected to the fluid conduit 107 foraspirating and injecting fluids. The tip configuration is discussed inmore detail below. The fluid delivery device 108, fluid conduit 107 andhollow needle form a fluid delivery system which enables fluid to beaspirated from, and a substance to be injected into, a target area.Different fluid delivery devices 108 can be connected to the fluidconduit 107, depending on the fluid to be aspirated or the substance tobe injected.

The structure of the distal assembly 118 may be arranged to have amaximum outer diameter suitable for passing through the working channel.Typically, the diameter of a working channel in a surgical scopingdevice such as an endoscope is less than 4.0 mm, e.g. any one of 2.8 mm,3.2 mm, 3.7 mm, 3.8 mm. The length of the flexible shaft 112 can beequal to or greater than 1.2 m, e.g. 2 m or more. In other examples, thedistal assembly 118 may be mounted at the distal end of the flexibleshaft 112 after the shaft has been inserted through the working channel(and before the instrument cord is introduced into the patient).Alternatively, the flexible shaft 112 can be inserted into the workingchannel from the distal end before making its proximal connections. Inthese arrangements, the distal end assembly 118 can be permitted to havedimensions greater than the working channel of the surgical scopingdevice 114.

The apparatus described above is one way of introducing the device.Other techniques are possible. For example, the device may also beinserted using a catheter.

The invention seeks to provide a device that can ablate a growth byapplying microwave energy directly to the growth tissue and/or via asubstance which is injected into the growth. The device is particularlysuited to the ablation of growths in the pancreas, such as cysts ortumours, however it may also be used to ablate growths in other organs.In order to ablate a growth, the microwave antenna and hollow needleshould be located as close as possible to (and in many cases inside) thetarget growth. In order to reach the pancreas, the device will thereforeneed to be guided through the digestive tract and around variousobstacles. This means that the device will ideally be flexible and havea small cross section. Particularly, the device should be very flexiblenear its tip, where it may need to be steered to cut through theduodenal wall to gain access to the pancreas. The distal assembly 118may also include an ultrasound probe (not shown), which is used toproduce images of the distal assembly's local environment, in order tofacilitate the guiding and positioning of the device inside a patient.The ultrasound probe is particularly useful for procedures involving theablation of a pancreatic cyst or tumour, as it enables the user todetermine the best location in the lower stomach or duodenum for makingan incision to access the pancreatic cyst/tumour.

It is also preferable that the device can be operated alongside otherinstruments to enable practitioners to receive information from thetarget site. For example, an endoscope may aid the steering of theinstruments around obstacles and to a desired position. Otherinstruments may include a thermometer or camera.

FIG. 2 is a schematic cross-sectional view of a distal end of a growthablation device 200 that is an embodiment of the invention. The growthablation device 200 includes an electrosurgical instrument 201 and afluid delivery system 202.

Electrosurgical instrument 201 includes a coaxial feed cable 204 that isconnected at its proximal end to a generator (such as generator 102) inorder to convey microwave energy. The coaxial feed cable 204 comprisesan inner conductor 206, which is separated from an outer conductor 208by a first dielectric material 210. The coaxial feed cable 204 ispreferably low loss for microwave energy. A choke (not shown) may beprovided on the coaxial cable to inhibit back propagation of microwaveenergy reflected from the distal end and therefore limit backwardheating along the device.

The coaxial feed cable 204 terminates at its distal end with a radiatingtip section 205 for radiating microwave energy. In this embodiment, theradiating tip section 205 comprises a distal conductive section 212 ofthe inner conductor 206 that extends before a distal end 209 of theouter conductor 208. The distal conductive section 212 is surrounded atits distal end by a dielectric tip 214 formed from a second dielectricmaterial, which is different from the first dielectric material 210. Thelength of the dielectric tip 214 is shorter than the length of thedistal conductive section 212. An intermediate dielectric sleeve 216surrounds the distal conductive section 212 between the distal end ofthe coaxial cable 202 and the proximal end of the dielectric tip 214.The intermediate dielectric sleeve 216 is formed from a third dielectricmaterial, which is different from the second dielectric material butwhich may be the same as the first dielectric material 210. Thedielectric tip 214 may have any suitable distal shape. In FIG. 2 it hasa dome shape, but this is not necessarily essential. For example, it maybe cylindrical, conical, etc. However, a smooth dome shape may bepreferred because it increases the mobility of the antenna as it ismanoeuvred through small channels. The electrosurgical instrument 201 ishoused in a protective sheath 218 which electrically insulates theelectrosurgical instrument 201. The protective sheath 218 may be madeof, or coated with, a non-stick material such as PTFE to prevent tissuefrom sticking to the instrument.

The properties of the intermediate dielectric sleeve 216 are preferablychosen (e.g. through simulation or the like) so that the radiating tipsection 205 forms a quarter wave impedance transformer for matching theinput impedance of the generator into a substance (e.g. injectedsubstance) and/or biological tissue load in contact with the radiatingtip section 205. This configuration of the radiating tip section 205 mayproduce an approximately spherical radiation pattern about the radiatingtip section 205. This enables the user to accurately radiate targettissue and reduces radiation of or damage to healthy tissue. Dependingon the radiation pattern required, different radiating tip sectionconfigurations may be used. For example, an asymmetric radiation patterncan be produced by extending the outer conductor 208 along one side ofthe radiating tip section 205.

The fluid delivery mechanism 202 includes a hollow needle 220 and afluid conduit 222. An end of the hollow needle 220 is disposed withinthe fluid conduit 222 such that the two are fluidly connected. Thehollow needle 220 is movable within the fluid conduit 222 along itslength. The fit between the outer wall of the hollow needle 220 and theinner wall of the fluid conduit 222 may be sufficiently tight such thatthere are no leakages when the hollow needle 220 is moved. The hollowneedle is moved using a control wire 224 which passes through the fluidconduit 222 and is attached to one end of the hollow needle 220. Theneedle may be fully or partially retracted into the fluid conduit 222,so that its sharp tip 226 does not protrude beyond the distal end of thegrowth ablation device 200. The fluid conduit 222 may include a valve(not shown) which prevents fluid from leaking out of, or into, the fluidconduit 222 when the hollow needle is in its retracted position. Whenthe user wishes to use the hollow needle (e.g. for piercing tissue orinjecting/aspirating fluid), the hollow needle 220 can be exposed suchthat it protrudes beyond the end of the growth ablation device 200. Thefluid delivery mechanism 202 may be fixed relative to theelectrosurgical instrument 201, so that the two components form a singleintegrated device which is configured to fit in the working channel ofan endoscope. For example the fluid conduit 222 may be secured to theprotective sheath 218 of the electrosurgical instrument 201.

Alternative ways of connecting the hollow needle 220 to the fluidconduit 222 and moving the hollow needle 220 relative to the distal endof the growth ablation device 200 are also possible. For example, thehollow needle 220 may be fixedly connected to the fluid conduit 222. Thefluid conduit 222 may then be disposed inside a sleeve through which thefluid conduit 222 and hollow needle 220 may be slid back and forth usinga control wire.

The growth ablation device 200 in FIG. 2 also includes an ultrasoundprobe 228 located near its distal end. The ultrasound probe 228 can beconnected to a power supply and monitor (not shown) using wiring 230.The ultrasound probe 230 can be used to produce images of theenvironment in the vicinity of the distal end of the growth ablationdevice 200. This enables the distal end of the growth ablation device200 to be accurately guided to a target location. Other components mayalso be included near the distal end of the growth ablation device 200.The growth ablation device 200 may include a temperature sensor tomonitor the local temperature when microwave energy is applied. Thegrowth ablation device 200 may also include a retractable blade near itsdistal end for performing incisions. For example, the retractable bladecan be exposed in order to make an incision in the lower stomach orduodenal wall in order to access the pancreas. When the blade is not inuse, the blade may be retracted so that its sharp edge is not exposed,in order to avoid accidental injuries when the growth ablation device200 is being guided into position.

In some embodiments, the growth ablation device 200 may also include anouter sheath in which the components at the distal end of the device arehoused. The outer sheath may have one or more apertures through whichthe hollow needle 220 and/or retractable blade may protrude. The outersheath may have a smooth shape so that no sharp corners are presented tobiological tissue, in order to avoid accidental injuries.

FIG. 3 is a schematic cross-sectional view of a distal end of a growthablation device 300 that is another embodiment of the invention. In thisembodiment, the fluid delivery system forms part of the electrosurgicalinstrument. The growth ablation device 300 includes a coaxial feed cable301, which can be connected at its proximal end to a generator (e.g.generator 102) in order to convey microwave energy. The coaxial feedcable 301 comprises an inner conductor 303, which is separated from anouter conductor 304 by a first dielectric material 306. The coaxial feedcable 301 is preferably low loss for microwave energy. A choke (notshown) may be provided on the coaxial cable to inhibit back propagationof microwave energy reflected from the distal end and therefore limitbackward heating along the device.

The coaxial feed cable 301 terminates at its distal end with a radiatingtip section 302 for radiating microwave energy. In this embodiment, theradiating tip section 302 comprises a distal conductive section 308 ofthe inner conductor 303 that extends before a distal end 309 of theouter conductor 304. The inner conductor 303 is hollow, with an innersurface of the inner conductor defining a channel 312 running throughthe inner conductor 303. The distal conductive section 308 is surroundedat its distal end by a dielectric tip 310 formed from a seconddielectric material, which is different from the first dielectricmaterial 306. The dielectric tip 310 is dome-shaped and has a channelrunning through it, and through which the inner conductor 303 passes. Anaperture 314 is formed at the distal end of the inner channel 303.

The channel 312 in the inner conductor 303 can be connected at aproximal end to a fluid delivery device (e.g. a syringe or container) sothat the channel 312 may act as a fluid conduit of a fluid deliverysystem. A hollow needle 318 is located inside the channel 312. Thehollow needle 318 has a first end 320 to which a guide wire 321 isattached, and a second end having a sharp tip 322 for piercingbiological tissue. The guide wire 321 is used to move the hollow needle318 back and forth along the length of the channel 312. A plug 316 islocated in the aperture 314 of the channel 312. The plug 316 isresiliently deformable to enable formation of a fluid tight seal withthe inner surface of the inner conductor 303. Plug 314 has an aperturerunning through it, through which the hollow needle 318 can be passed.Using the guide wire 321, the hollow needle 318 can be passed throughplug 316, so that the sharp tip 322 of the hollow needle 318 protrudesfrom the plug 316. The hollow needle 318 is then in an exposed position.In this position, when a liquid is fed to the first end 320 of thehollow needle 318, via the channel 312, it can exit through the tip 322of the hollow needle to the surrounding area, for treatment orotherwise. Similarly, liquid may be aspirated through the hollow needle318 into the channel 312.

By pulling the guide wire 321, the hollow needle 318 can be retractedsuch that its tip 322 is situated inside the channel 312 and so nolonger exposed to the surrounding area. This is the retracted position.When the hollow needle 318 is in this position, the resilientlydeformable nature of the plug 316 ensures that it seals itself,preventing liquid inside the channel 312 from escaping to thesurroundings, and preventing liquid or other matter from thesurroundings from entering channel 312 and contaminating its contents.The plug 316 may include a one-way valve that permits passage of theneedle.

Similarly to the growth ablation device shown in FIG. 2 , growthablation device 300 may include other components such as an ultrasoundprobe, a temperature sensor or a retractable blade. Growth ablationdevice 300 may also include a protective outer sheath, for example madeof a biologically inert material. Other growth ablation deviceconfigurations, other than those shown in FIGS. 2 and 3 are possible.

FIG. 4 shows a schematic illustration of growth tissue ablation using agrowth ablation device according to the invention. A growth ablationdevice 400, such as the devices depicted in FIGS. 2 and 3 is insertedinto a void in a growth 402. Using the fluid delivery system of thegrowth ablation device 400, any fluid in the void 402 is aspirated, e.g.by connecting a proximal end of the fluid conduit to an suitableaspiration or fluid extraction apparatus.

Where the growth ablation device 200 shown in FIG. 2 is used, hollowneedle 220 is moved forward using the guide wire 224 so that it is in anexposed position. The hollow needle 220 is used to pierce through thewall of the void 402. The fluid is then aspirated through the fluidconduit 222 via the hollow needle 220, and collected in a collectioncontainer (not shown) connected at the proximal end of the fluid conduit222. A similar procedure may be carried out with growth ablation device300.

Once the fluid in the void 402 has been aspirated, the fluid deliverysystem is then used to inject a substance into the void. The volume ofsubstance injected into the void 402 may be the same as the volume offluid aspirated. This is achieved, for example, by measuring the volumeof fluid in the collection container and setting the injection volumeaccordingly. The injection is performed with the hollow needle 220 stillin the exposed position, by causing the substance to flow from asubstance container connected to the proximal end of the fluid conduit222 into the void 402 via the fluid conduit 222 and hollow needle 220.The connections between the containers and fluid conduit are discussedbelow in relation to FIG. 5 .

FIG. 4 shows the void 402 once a substance 404 has been injected intothe void. The substance 404 is depicted as the shaded area. Afterinjection of the substance 404, the electrosurgical instrument is usedto apply microwave energy to the substance. To do this the radiating tipportion (i.e. the microwave antenna) of the electrosurgical instrumentis placed as near as possible to the substance 404. Preferably theradiating tip portion is inserted directly into the void 402 such thatit is in contact with the injected substance. Microwave energy is thentransmitted to the radiating tip portion via the coaxial feed cable,such that microwave energy radiates from the tip into the substance.

The substance facilitates delivery of treatment energy to biologicaltissue at the inner surface of the void or growth. This can be done inany of three ways. In one example, the substance presents a thermallyconductive medium that assists in the transformation of microwave energyinto thermal energy and the communication or transmission of thatthermal energy to the biological tissue. In another example, thesubstance acts as an extension to the radiating tip, so that themicrowave energy is radiated at the interface between the substance andthe biological tissue. In a third example, the substance acts as adielectric load for the radiating tip. The properties of the substancemay be selected to ensure efficient transfer of the microwave energyfrom the radiating tip to the biological tissue.

The treatment energy applied to the walls of the void 402 can causeablation of biological tissue. The transmission of energy is illustratedby radiating lines 406 in FIG. 4 .

The void 402 in FIG. 4 is non-symmetrical and has a highly irregularshape. In the absence of any substance injected into the void 402, someportions of the void walls could receive a lower intensity of radiationcompared to other portions as they are further away from the radiatingtip portion of the electrosurgical instrument. This could lead to unevenablation of growth tissue around the void, or even some parts of thegrowth being left substantially unaffected. The substance 404 serves todistribute the energy radiated by the growth ablation device 400 moreevenly across the walls of the void 402, so as to provide effectiveablation of growth tissue around the entire void 402.

As discussed above, the manner in which the substance transmits energyto the growth tissue depends on the substance used. In some cases, thesubstance may be a dielectric fluid (e.g. liquid paraffin, acetophenone)which serves to dielectrically load the antenna when the antenna isinserted into the substance. This can improve the efficiency of powerdelivery to the growth tissue.

In other cases, the substance can form part of the microwave antennatip, in order to produce a non-symmetrical radiation profile in order tomatch the shape of the void.

In yet further cases, the substance may have a high dielectric lossfactor at the microwave energy frequency used, whereby the substancewill heat up with microwave energy is applied to it. Any generated heatin the substance will be distributed throughout the substance via heatconduction processes. Where the substance is in contact with the wallsof the void, thermal energy will be transmitted from the substance tothe tissue in the wall. This causes heat to be applied evenly across thewalls of the void. De-ionised water and/or saline can be used for thispurpose. In contrast, if the substance has a low dielectric loss factorat the microwave energy frequency, it may act as a means fromtransmitting microwave from the antenna to the walls of the void.

In some cases the substance may include materials which are liquid whenthey are injected, but which will harden or solidify when microwaveenergy is applied to them. The hardening may occur due to an increase intemperature caused by the microwave energy. Preferably such a substancewill have a low dielectric loss factor at the microwave energyfrequency. Example substances having such properties are Kolliphor® P188 and Kolliphor® P 407.

It should be noted that the growth ablation device of the presentinvention may be used in a mode where no substance is injected into thevoid. For example, fluid may be aspirated from the void, and themicrowave antenna may be inserted into the void (without having injectedany substance) to apply microwave energy directly to the void walls. Thegrowth ablation device may also be used to ablate solid growths (i.e.growths which do not have a void), by inserting the microwave antennadirectly into the solid growth and applying microwave energy. The growthablation device of the invention is therefore highly flexible, as it canbe used in a variety of different modes, and to ablate different typesof growth, depending on the requirements of a particular procedure.

FIG. 5 is a schematic diagram of a fluid delivery system 500 which canbe used as part of a growth ablation device according to the invention.The fluid delivery mechanism 500 may be integrated with anelectrosurgical instrument, for example as discussed in relation to FIG.2 or 3 , in order to form a growth ablation device. The fluid deliverysystem 500 includes a fluid conduit 502. At its distal end, the fluidconduit 502 is fluidly connected to a hollow needle 504. At its proximalend, the fluid conduit 502 is connected to a T-junction 506. Acollection syringe 508 is connected to a first end of the T-junction,and a substance syringe 510 is connected to a second end of theT-junction. The collection syringe 508 can be connected to the fluidconduit 502 by opening valve 512 which is located between the first endof the T-junction 506 and the fluid conduit 502. The substance syringe510 can be connected to the fluid conduit by opening valve 514 which islocated between the second end of the T-junction 506 and the fluidconduit 502.

Thus, when fluid is to be aspirated from a void in a growth, valve 514is closed and valve 512 is opened, such that the collection syringe 508is fluidly connected to the hollow needle 504 via the fluid conduit 502.Fluid located near the tip of the hollow needle 504 can be aspiratedinto the collection syringe 508 using the piston of the syringe. When asubstance is to be injected, valve 512 is closed and valve 514 isopened, such that substance syringe 510 is fluidly connected to thehollow needle 504 via the fluid conduit 502. A volume of substance canthen be injected from the substance syringe 510 into a target area viathe hollow needle 504. The valves and syringes may be controlledmanually or automatically (e.g. using a controller), so that use of thefluid delivery mechanism 502 may be substantially automated.

In alternative configurations, the fluid conduit 502 may not beconnected to a T-junction. In this case, the syringes can be connecteddirectly to the proximal end of the fluid conduit, and must be exchangeddepending on the operation to be carried out (i.e. fluid aspiration orsubstance injection). Other suitable fluid delivery mechanisms otherthan syringes may be used. For example, a container coupled to a pumpcould be used for collecting and/or injecting fluid.

1. An electrosurgical apparatus for treating a biological growth thatcontains a fluid-filled sac, the apparatus comprising: anelectrosurgical instrument for delivering microwave energy intobiological tissue, the electrosurgical instrument comprising: a coaxialcable for conveying microwave energy; and a radiating tip portiondisposed at a distal end of the coaxial cable to receive microwaveenergy from the coaxial cable; and a fluid delivery mechanism fortransporting fluid to and from a treatment zone located around theradiating tip portion, wherein the fluid delivery mechanism comprises: aflexible fluid conveying conduit that extends along the coaxial cable,and a rigid insertion element in fluid communication with a distal endof the fluid conveying conduit and arranged to extend into the treatmentzone, wherein the fluid delivery mechanism is arranged: to aspiratefluid from the treatment zone, and to inject a substance into thetreatment zone to replace the aspirated fluid, and wherein the substancehas dielectric properties selected to facilitate uniform delivery oftreatment energy to biological tissue in the treatment zone, and whereinthe substance is selected to transition from a liquid phase to a solidphase during application of microwave energy to the treatment zone. 2.An electrosurgical apparatus according to claim 1, wherein the treatmentzone includes a fluid-filled sac contained within a biological growth,whereby the fluid delivery mechanism is arranged to replace biologicalfluid in the fluid-filled sac with the substance.
 3. An electrosurgicalapparatus according to claim 1, wherein the fluid delivery mechanism isarranged to inject a volume of the substance into the treatment zonethat is equal to a volume of the fluid aspirated from the treatmentzone.
 4. An electrosurgical apparatus according to claim 1, wherein thesubstance consists of a dielectric fluid.
 5. An electrosurgicalapparatus according to claim 1, wherein the substance comprisesde-ionised water or saline.
 6. An electrosurgical apparatus according toclaim 1, wherein the substance extends the radiating tip portion.
 7. Anelectrosurgical apparatus according to claim 1, wherein the rigidinsertion element is in fluid communication with the flexible fluidconveying conduit via a passageway.
 8. An electrosurgical apparatusaccording to claim 7, wherein the rigid insertion element is slidablymounted in the passageway.
 9. An electrosurgical apparatus according toclaim 1, wherein the rigid insertion element is movable between anexposed position where it protrudes beyond the distal end of theelectrosurgical instrument, and a retracted position in which it is setback from the distal end of the electrosurgical instrument.
 10. Anelectrosurgical apparatus according to claim 1, wherein theelectrosurgical instrument comprises an ultrasound probe for producingimages of a patient's internal organs.
 11. An electrosurgical apparatusaccording to claim 1, further comprising: a generator for generating themicrowave energy; and a surgical scoping device for non-percutaneousinsertion into a patient's digestive tract, the surgical scoping devicehaving an instrument channel running along its length, wherein theelectrosurgical instrument and fluid delivery mechanism are conveyedwithin the instrument channel of the surgical scoping device, andwherein the coaxial cable is connected to receive the microwave energyfrom the generator.